Polyurethane urea polishing pad

ABSTRACT

The present invention relates to an article for altering a surface of a workpiece, or a polishing pad having a window. In particular, the polishing pad includes a polyurethane urea material wherein the polyurethane urea material contains cells which are at least partially filled with gas. The polyurethane urea material can be prepared by combining polyisocyanate and/or polyurethane prepolymer, hydroxyl-containing material, amine-containing material and blowing agent. The polishing pad according to the present invention is useful for polishing articles, and is especially useful for chemical mechanical polishing or planarization of microelectronic and optical electronic devices such as but not limited to semiconductor wafers. The window of the polishing pad is at least partially transparent and thus, can be particularly useful with polishing or planarizing tools that are equipped with through-the-platen wafer metrology.

The present invention relates to an article for altering a surface of aworkpiece. In particular, the present invention is directed to apolishing pad having a window. More particularly, the polishing pad caninclude a polyurethane urea material wherein cells at least partiallyfilled with gas are substantially uniformly distributed throughout thematerial and/or pad. The polyurethane urea material can be prepared bycombining polyisocyanate and/or polyurethane prepolymer;hydroxyl-containing material; amine-containing material and blowingagent. The polishing pad according to the present invention is usefulfor polishing articles, and is especially useful for chemical mechanicalpolishing or planarization of microelectronic and optical electronicdevices such as but not limited to semiconductor wafers. The window ofthe polishing pad is at least partially transparent and thus, can beparticularly useful with polishing or planarizing tools that areequipped with through-the-platen wafer metrology.

The polishing or planarization of a rough surface of an article such asa microelectronic device, to a substantially smooth surface generallyinvolves rubbing the rough surface with the work surface of a polishingpad using a controlled and repetitive motion. A polishing fluid can beinterposed between the rough surface of the article that is to bepolished and the work surface of the polishing pad.

The fabrication of a microelectronic device can comprise the formationof a plurality of integrated circuits on a semiconductor substrate. Thecomposition of the substrate can include silicon or gallium arsenide.The integrated circuits generally can be formed by a series of processsteps in which patterned layers of materials, such as conductive,insulating and semi-conducting materials, are formed on the substrate.In order to maximize the density of integrated circuits per wafer, it isdesirable to have a planar polished substrate at various stagesthroughout the production process. As such, production of amicroelectronic device typically involves at least one polishing stepand can often involve a plurality of polishing steps, which can resultin the use of more than one polishing pad.

The polishing step can include rotating the polishing pad and thesemiconductor substrate against each other in the presence of apolishing fluid. The polishing fluid can be mildly alkaline and canoptionally contain an abrasive particulate material such as but notlimited to particulate cerium oxide, particulate alumina, or particulatesilica. The polishing fluid can facilitate the removal and transport ofabraded material off and away from the rough surface of the article.

Polishing pad characteristics such as pore volume and pore size can varyfrom pad-to-pad and throughout the operating lifetime of a particularpad. Variations in the polishing characteristics of the pads can resultin inadequately polished and planarized substrates which can beunsuitable for fabricating semiconductor wafers. Thus, it is desirableto develop a polishing pad that exhibits reduced pad-to-pad variation inpolishing and planarization characteristics. It is further desirable todevelop a polishing pad that exhibits reduced variations in polishingand planarization characteristics throughout the operating lifetime ofthe pad.

Planarizing tools having the ability to measure the progress of theplanarization process while the wafer is held in the tool and in contactwith the pad are known in the art. Measuring the progress of planarizinga microelectronic device during the planarizing process can be referredto in the art as “in-situ metrology”. U.S. Pat. Nos. 5,964,643 and6,159,073; and European Patent 1,108,501 describe polishing orplanarizing tools and in-situ metrology systems. In general, in-situmetrology can include directing a beam of light through an at leastpartially transparent window located in the platen of the tool; the beamof light can be reflected off the surface of the wafer, back through theplaten window, and into a detector. The polishing pad can include awindow that is at least partially transparent to the wavelengths used inthe metrology system, and essentially aligned with the planten window.

Thus, it is desirable to develop a polishing pad that comprises a windowarea useful for in-situ metrology. It is further desirable that thewindow provides suitable transparency throughout the operating life ofthe pad.

One disadvantage with known pads having windows which are coplanar withthe polishing surface, can include wearing of the window portion at aslower rate than the pad surface. A further disadvantage with known padshaving a coplanar window can include scratching of the window as aresult of its contact with abrasive particles in the slurry during thepolishing or planarization process. A scratched window can generallyreduce the transparency of the window and can cause an attenuation ofthe metrology signal.

For the purposes of this specification, unless otherwise indicated, allnumbers expressing quantities of ingredients, reaction conditions, andso forth used in the specification and claims are to be understood asbeing modified in all instances by the term “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

The present invention includes a pad having an at least partiallytransparent cast-in-place window adapted to polish a microelectronicsubstrate. The pad of the present invention comprises polyurethane ureamaterial. At least a portion of the polyurethane urea contains cellsthat are at least partially filled with gas, and at least a portion ofthe at least partially gas-filled cells is formed by an in-situreaction.

In a non-limiting embodiment, the cells can be substantially uniformlydistributed throughout the material and/or pad. In another non-limitingembodiment, the polyurethane urea can be prepared by combiningpolyisocyanate, hydroxyl-containing material, amine-containing materialand blowing agent. In another non-limiting embodiment, the polyurethaneurea can be formed by condensation polymerization of polyisocyanatefunctional polyurethane prepolymer with polyamine and blowing agent. Ina further non-limiting embodiment, the polyurethane urea can be formedby combining polyisocyanate and polyurethane prepolymer, optionalhydroxyl-containing material, amine-containing material and blowingagent. In a non-limiting embodiment, at least a portion of the pad cancomprise a window which is at least partially transparent to wavelengthsused by the metrology instrumentation of polishing tools.

In alternate non-limiting embodiments, the amount of polyisocyanate,hydroxyl-containing material and amine-containing material can beselected such that the equivalent ratio of (NCO+NCS):(NH+OH) can begreater than 0.95, or at least 1.0, or at least 1.05, or less than 1.3,or less than 1.2, or less than 1.1.

Polyisocyanates useful in the preparation of the polyurethane urea ofthe present invention are numerous and widely varied. Suitablepolyisocyanates can include but are not limited to polymeric and C₂-C₂₀linear, branched, cyclic and aromatic polyisocyanates. Non-limitingexamples can include polyisocyanates having backbone linkages chosenfrom urethane linkages (—NH—C(O)—O—).

The molecular weight of the polyisocyanate can vary widely. In alternatenon-limiting embodiments, the number average molecular weight (Mn) canbe at least 100 grams/mole, or at least 150 grams/mole, or less than15,000 grams/mole, or less than 5000 grams/mole. The number averagemolecular weight can be determined using known methods. The numberaverage molecular weight values recited herein and the claims weredetermined by gel permeation chromatography (GPC) using polystyrenestandards.

Non-limiting examples of suitable polyisocyanates can include but arenot limited to polyisocyanates having at least two isocyanate groups.

Non-limiting examples of polyisocyanates can include but are not limitedto aliphatic polyisocyanates, cycloaliphatic polyisocyanates wherein oneor more of the isocyanato groups are attached directly to thecycloaliphatic ring, cycloaliphatic polyisocyanates wherein one or moreof the isocyanato groups are not attached directly to the cycloaliphaticring, aromatic polyisocyanates wherein one or more of the isocyanatogroups are attached directly to the aromatic ring, and aromaticpolyisocyanates wherein one or more of the isocyanato groups are notattached directly to the aromatic ring.

In a non-limiting embodiment of the present invention, thepolyisocyanate can include but is not limited to aliphatic orcycloaliphatic diisocyanates, aromatic diisocyanates, cyclic dimers andcyclic trimers thereof, and mixtures thereof. Non-limiting examples ofsuitable polyisocyanates can include but are not limited to Desmodur N3300A (hexamethylene diisocyanate trimer) which is commerciallyavailable from Bayer; Desmodur N 3400 (60% hexamethylene diisocyanatedimer and 40% hexamethylene diisocyanate trimer).

In a non-limiting embodiment, the polyisocyanate can includedicyclohexylmethane diisocyanate and isomeric mixtures thereof. As usedherein and the claims, the term “isomeric mixtures” refers to a mixtureof the cis-cis, trans-trans, and cis-trans isomers of thepolyisocyanate. Non-limiting examples of isomeric mixtures for use inthe present invention can include the trans-trans isomer of4,4″-methylenebis(cyclohexyl isocyanate), hereinafter referred to as“PICM” (paraisocyanato cyclohexylmethane), the cis-trans isomer of PICM,the cis-cis isomer of PICM, and mixtures thereof.

In one non-limiting embodiment, the PICM used in this invention can beprepared by phosgenating the 4,4′-methylenebis(cyclohexyl amine) (PACM)by procedures well known in the art such as the procedures disclosed inU.S. Pat. Nos. 2,644,007 and 2,680,127 which are incorporated herein byreference. The PACM isomer mixtures, upon phosgenation, can produce PICMin a liquid phase, a partially liquid phase, or a solid phase at roomtemperature. The PACM isomer mixtures can be obtained by thehydrogenation of methylenedianiline and/or by fractional crystallizationof PACM isomer mixtures in the presence of water and alcohols such asmethanol and ethanol.

In a non-limiting embodiment, the isomeric mixture can contain from10-100 percent of the trans,trans isomer of 4,4′-methylenebis(cyclohexylisocyanate) (PICM).

In a non-limiting embodiment, the polyisocyanate can include2,4-tolylene diisocyanate; 2,6-tolylene diisocyanate and mixtures ofthese isomers (“TDI”).

Additional aliphatic and cycloaliphatic diisocyanates that can be usedin alternate non-limiting embodiments of the present invention include3-isocyanato-methyl-3,5,5-trimethyl cyclohexyl-isocyanate (“IPDI”) whichis commercially available from Arco Chemical, and meta-tetramethylxylenediisocyanate (1,3-bis(1-isocyanato-1-methylethyl)-benzene) which iscommercially available from Cytec Industries Inc. under the tradenameTMXDI.RTM. (Meta) Aliphatic Isocyanate.

As used herein and the claims, the terms aliphatic and cycloaliphaticdiisocyanates refer to 6 to 100 carbon atoms linked in a straight chainor cyclized having two diisocyanate reactive end groups. In anon-limiting embodiment of the present invention, the aliphatic andcycloaliphatic diisocyanates for use in the present invention caninclude TMXDI and compounds of the formula R—(NCO)₂ wherein R representsan aliphatic group or a cycloaliphatic group.

Further non-limiting examples of suitable polyisocyanates can includebut are not limited to aliphatic polyisocyanates; ethylenicallyunsaturated polyisocyanates; alicyclic polyisocyanates; aromaticpolyisocyanates wherein the isocyanate groups are not bonded directly tothe aromatic ring, e.g., α,α′-xylene diisocyanate; aromaticpolyisocyanates wherein the isocyanate groups are bonded directly to thearomatic ring, e.g., benzene diisocyanate;halogenated, alkylated,alkoxylated, nitrated, carbodiimide-modified, urea-modified andbiuret-modified derivatives of polyisocyanates thereof; and dimerizedand trimerized products of polyisocyanates thereof.

Further non-limiting examples of aliphatic polyisocyanates can includeethylene diisocyanate, trimethylene diisocyanate, tetramethylenediisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate,nonamethylene diisocyanate, 2,2′-dimethylpentane diisocyanate,2,2,4-trimethylhexane diisocyanate, decamethylene diisocyanate,2,4,4,-trimethylhexamethylene diisocyanate,1,6,11-undecanetriisocyanate, 1,3,6-hexamethylene triisocyanate,1,8-diisocyanato-4-(isocyanatomethyl)octane,2,5,7-trimethyl-1,8-diisocyanato-5-(isocyanatomethyl)octane,bis(isocyanatoethyl)-carbonate, bis(isocyanatoethyl)ether,2-isocyanatopropyl-2,6-diisocyanatohexanoate, lysinediisocyanate methylester and lysinetriisocyanate methyl ester.

Examples of ethylenically unsaturated polyisocyanates can include butare not limited to butene diisocyanate and1,3-butadiene-1,4-diisocyanate. Alicyclic polyisocyanates can includebut are not limited to isophorone diisocyanate, cyclohexanediisocyanate, methylcyclohexane diisocyanate, bis(isocyanatomethyl)cyclohexane, bis(isocyanatocyclohexyl)methane,bis(isocyanatocyclohexyl)-2,2-propane,bis(isocyanatocyclohexyl)-1,2-ethane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptaneand2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane.

Examples of aromatic polyisocyanates wherein the isocyanate groups arenot bonded directly to the aromatic ring can include but are not limitedto bis(isocyanatoethyl)benzene, α,α,α′,α′-tetramethylxylenediisocyanate, 1,3-bis(1-isocyanato-1-methylethyl)benzene,bis(isocyanatobutyl)benzene, bis(isocyanatomethyl)naphthalene,bis(isocyanatomethyl)diphenyl ether, bis(isocyanatoethyl) phthalate,mesitylene triisocyanate and 2,5-di(isocyanatomethyl)furan. Aromaticpolyisocyanates having isocyanate groups bonded directly to the aromaticring can include but are not limited to phenylene diisocyanate,ethylphenylene diisocyanate, isopropylphenylene diisocyanate,dimethylphenylene diisocyanate, diethylphenylene diisocyanate,diisopropylphenylene diisocyanate, trimethylbenzene triisocyanate,benzene triisocyanate, naphthalene diisocyanate, methylnaphthalenediisocyanate, biphenyl diisocyanate, ortho-toluidine diisocyanate,ortho-tolylidine diisocyanate, ortho-tolylene diisocyanate,4,4′-diphenylmethane diisocyanate,bis(3-methyl-4-isocyanatophenyl)methane, bis(isocyanatophenyl)ethylene,3,3′-dimethoxy-biphenyl-4,4′-diisocyanate, triphenylmethanetriisocyanate, polymeric 4,4′-diphenylmethane diisocyanate, naphthalenetriisocyanate, diphenylmethane-2,4,4′-triisocyanate,4-methyldiphenylmethane-3,5,2′,4′,6′-pentaisocyanate, diphenyletherdiisocyanate, bis(isocyanatophenylether)ethyleneglycol,bis(isocyanatophenylether)-1,3-propyleneglycol, benzophenonediisocyanate, carbazole diisocyanate, ethylcarbazole diisocyanate anddichlorocarbazole diisocyanate.

In alternate non-limiting embodiments of the present invention,polyisothiocyanate or a combination of polyisocyanate andpolyisothiocyanate can be used in place of polyisocyanate. In thesealternate non-limiting embodiments, isothiocyanate can have at least twoisothiocyanate groups.

In a non-limiting embodiment of the present invention, thepolyisocyanate for use in the present invention can include polyurethaneprepolymer.

In a non-limiting embodiment, polyisocyanate can be reacted withhydroxyl-containing material to form polyurethane prepolymer.Hydroxyl-containing materials are varied and known in the art.Non-limiting examples can include but are not limited to polyols;sulfur-containing materials such as but not limited to hydroxylfunctional polysulfides, and SH-containing materials such as but notlimited to polythiols; and materials having both hydroxyl and thiolfunctional groups.

Suitable hydroxyl-containing materials for use in the present inventioncan include a wide variety of materials known in the art. Non-limitingexamples can include but are not limited to polyether polyols, polyesterpolyols, polycaprolactone polyols, polycarbonate polyols, and mixturesthereof.

Polyether polyols and methods for their preparation are known to oneskilled in the art. Many polyether polyols of various types andmolecular weight are commercially available from various manufacturers.Non-limiting examples of polyether polyols can include but are notlimited to polyoxyalkylene polyols, and polyalkoxylated polyols.Polyoxyalkylene polyols can be prepared in accordance with knownmethods. In a non-limiting embodiment, a polyoxyalkylene polyol can beprepared by condensing an alkylene oxide, or a mixture of alkyleneoxides, using acid- or base-catalyzed addition with a polyhydricinitiator or a mixture of polyhydric initiators, such as but not limitedto ethylene glycol, propylene glycol, glycerol, and sorbitol.Non-limiting examples of alkylene oxides can include ethylene oxide,propylene oxide, butylene oxide, amylene oxide, aralkylene oxides, suchas but not limited to styrene oxide, mixtures of ethylene oxide andpropylene oxide. In a further non-limiting embodiment, polyoxyalkylenepolyols can be prepared with mixtures of alkylene oxide using random orstep-wise oxyalkylation. Non-limiting examples of such polyoxyalkylenepolyols include polyoxyethylene, such as but not limited to polyethyleneglycol, polyoxypropylene, such as but not limited to polypropyleneglycol.

In a non-limiting embodiment, polyalkoxylated polyols can be representby the following general formula:

wherein m and n can each be a positive integer, the sum of m and n beingfrom 5 to 70; R₁ and R₂ are each hydrogen, methyl or ethyl; and A is adivalent linking group such as a straight or branched chain alkylenewhich can contain from 1 to 8 carbon atoms, phenylene, and C₁ to C₉alkyl-substituted phenylene. The chosen values of m and n can, incombination with the chosen divalent linking group, determine themolecular weight of the polyol.

Polyalkoxylated polyols can be prepared by methods that are known in theart. In a non-limiting embodiment, a polyol such as4,4′-isopropylidenediphenol can be reacted with an oxirane-containingmaterial such as but not limited to ethylene oxide, propylene oxide andbutylene oxide, to form what is commonly referred to as an ethoxylated,propoxylated or butoxylated polyol having hydroxy functionality.Non-limiting examples of polyols suitable for use in preparingpolyalkoxylate polyols can include those polyols described in U.S. Pat.No. 6,187,444 B1 at column 10, lines 1-20, which disclosure isincorporated herein by reference.

As used herein and the claims, the term “polyether polyols” can includethe generally known poly(oxytetramethylene) diols prepared by thepolymerization of tetrahydrofuran in the presence of Lewis acidcatalysts such as but not limited to boron trifluoride, tin (IV)chloride and sulfonyl chloride. In a non-limiting embodiment, thepolyether polyol can include Terathane™ which is commercially availablefrom DuPont. Also included are the polyethers prepared by thecopolymerization of cyclic ethers such as but not limited to ethyleneoxide, propylene oxide, trimethylene oxide, and tetrahydrofuran withaliphatic diols such as but not limited to ethylene glycol,1,3-butanediol, 1,4-butanediol, diethylene glycol, dipropylene glycol,1,2-propylene glycol and 1,3-propylene glycol. Compatible mixtures ofpolyether polyols can also be used. As used herein, “compatible” meansthat the polyols are mutually soluble in each other so as to form asingle phase.

A wide variety of polyester polyols known in the art can be used in thepresent invention. Suitable polyester polyols can include but are notlimited to polyester glycols. Polyester glycols for use in the presentinvention can include the esterification products of one or moredicarboxylic acids having from four to ten carbon atoms, such as but notlimited to adipic, succinic or sebacic acids, with one or more lowmolecular weight glycols having from two to ten carbon atoms, such asbut not limited to ethylene glycol, propylene glycol, diethylene glycol,1,4-butanediol, neopentyl glycol, 1,6-hexanediol and 1,10-decanediol.Esterification procedures for producing polyester polyols is described,for example, in the article D. M. Young, F. Hostettler et al.,“Polyesters from Lactone,” Union Carbide F-40, p. 147.

In a non-limiting embodiment, the polyol for use in the presentinvention can include polycaprolactone polyols. Suitablepolycaprolactone polyols are varied and known in the art. In anon-limiting embodiment, polycaprolactone polyols can be prepared bycondensing caprolactone in the presence of difunctional active hydrogencompounds such as but not limited to water or low molecular weightglycols as recited herein. Non-limiting examples of suitablepolycaprolactone polyols can include commercially available materialsdesignated as the CAPA series from Solvay Chemical which includes but isnot limited to CAPA 2047A, and the TONE™ series from Dow Chemical suchas but not limited to TONE 0201.

Polycarbonate polyols for use in the present invention are varied andknown to one skilled in the art. Suitable polycarbonate polyols caninclude those commercially available (such as but not limited toRavecarb™ 107 from Enichem S. p. A.). In a non-limiting embodiment, thepolycarbonate polyol can be produced by reacting an organic glycol suchas a diol, described hereinafter and in connection with the glycolcomponent of the polyurethane or polyurethane urea, and a dialkylcarbonate, such as described in U.S. Pat. No. 4,160,853. In anon-limiting embodiment, the polyol can include polyhexamethyl carbonatesuch as HO—(CH₂)₆—[O—C(O)—O—(CH₂)₆]_(n)—OH, wherein n is an integer from4 to 24, or from 4 to 10, or from 5 to 7.

In a non-limiting embodiment, the glycol material can comprise lowmolecular weight polyols such as polyols having a number averagemolecular weight of less than 500 grams/mole, and compatible mixturesthereof. As used herein, the term “compatible” means that the glycolsare mutually soluble in each other so as to form a single phase.Non-limiting examples of these polyols can include but are not limitedto low molecular weight diols and triols. In a further non-limitingembodiment, the amount of triol chosen can be such to avoid a highdegree of cross-linking in the polyurethane or polyurethane urea. Inalternate non-limiting embodiments, the organic glycol can contain from2 to 16, or from 2 to 6, or from 2 to 10, carbon atoms. Non-limitingexamples of such glycols can include but are not limited to ethyleneglycol, propylene glycol, diethylene glycol, triethylene glycol,tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-,1,3- and 1,4-butanediol, 2,2,4-trimethyl-1,3-pentanediol,2-methyl-1,3-pentanediol, 1,3- 2,4- and 1,5-pentanediol, 2,5- and1,6-hexanediol, 2,4-heptanediol, 2-ethyl-1,3-hexanediol,2,2-dimethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol,1,10-decanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol,1,2-bis(hydroxyethyl)-cyclohexane, glycerin, tetramethylolmethane,pentaerythritol, trimethylolethane and trimethylolpropane; and isomersthereof.

In alternate non-limiting embodiments, the hydroxyl-containing materialcan have a molecular weight of at least 200 grams/mole, or at least 1000grams/mole, or at least 2000 grams/mole. In alternate non-limitingembodiments, the hydroxyl-containing material can have a number averagemolecular weight of less than 10,000 grams/mole, or less than 15,000grams/mole, or less than 20,000 grams/mole, or less than 32,000grams/mole.

In a non-limiting embodiment, the hydroxyl-containing material for usein the present invention can include teresters produced from at leastone low molecular weight dicarboxylic acid, such as adipic acid.

In a non-limiting embodiment, the hydroxyl-containing material cancomprise block polymers including blocks of ethylene oxide-propyleneoxide and/or ethylene oxide-butylene oxide. In a non-limitingembodiment, the hydroxyl-containing material can comprise a blockpolymer of the following chemical formula:HO—(O—CRRCRR—Y_(n))_(a)—(CRRCRR—Y_(n)—O)_(b)—(CRRCRR—Y_(n)—O)_(c)—H  (II)wherein R can represent hydrogen or C₁-C₆ alkyl; Y_(n) can representC₀-C₆ hydrocarbon; n can be an integer from 0 to 6; a, b, and c can eachbe an integer from 0 to 300, wherein a, b and c are chosen such that thenumber average molecular weight of the polyol does not exceed 32,000grams/mole.

In further alternate non-limiting embodiments, hydroxyl-containingmaterials such as but not limited to Pluronic.RTM R, Pluronic.RTM,Tetronic.RTM R and Tetronic.RTM Block Copolymer Surfactants, which arecommercially available from BASF, can be used as the hydroxyl-containingmaterial in the present invention.

Further non-limiting examples of suitable polyols for use in the presentinvention can include straight or branched chain alkane polyols, such asbut not limited to 1,2-ethanediol, 1,3-propanediol, 1,2-propanediol,1,4-butanediol, 1,3-butanediol, glycerol, neopentyl glycol,trimethylolethane, trimethylolpropane, di-trimethylolpropane,erythritol, pentaerythritol and di-pentaerythritol; polyalkyleneglycols, such as but not limited to diethylene glycol, dipropyleneglycol and higher polyalkylene glycols such as but not limited topolyethylene glycols which can have number average molecular weights offrom 200 grams/mole to 2,000 grams/mole; cyclic alkane polyols, such asbut not limited to cyclopentanediol, cyclohexanediol, cyclohexanetriol,cyclohexanedimethanol, hydroxypropylcyclohexanol andcyclohexanediethanol; aromatic polyols, such as but not limited todihydroxybenzene, benzenetriol, hydroxybenzyl alcohol anddihydroxytoluene; bisphenols, such as, 4,4′-isopropylidenediphenol;4,4′-oxybisphenol, 4,4′-dihydroxybenzophenone, 4,4′-thiobisphenol,phenolphthlalein, bis(4-hydroxyphenyl)methane,4,4′-(1,2-ethenediyl)bisphenol and 4,4′-sulfonylbisphenol; halogenatedbisphenols, such as but not limited to4,4′-isopropylidenebis(2,6-dibromophenol),4,4′-isopropylidenebis(2,6-dichlorophenol) and4,4′-isopropylidenebis(2,3,5,6-tetrachlorophenol); alkoxylatedbisphenols, such as but not limited to alkoxylated4,4′-isopropylidenediphenol which can have from 1 to 70 alkoxy groups,for example, ethoxy, propoxy, α-butoxy and β-butoxy groups; andbiscyclohexanols, which can be prepared by hydrogenating thecorresponding bisphenols, such as but not limited to4,4′-isopropylidene-biscyclohexanol, 4,4′-oxybiscyclohexanol,4,4′-thiobiscyclohexanol and bis(4-hydroxycyclohexanol)methane;polyurethane or polyurethane urea polyols, polyester polyols, polyetherpolyols, poly vinyl alcohols, polymers containing hydroxy functionalacrylates, polymers containing hydroxy functional methacrylates, andpolymers containing allyl alcohols.

In a non-limiting embodiment, the polyol can be chosen frommultifunctional polyols, including but not limited totrimethylolpropane, ethoxylated trimethylolpropane, pentaerythritol.

In alternate non-limiting embodiments, the polyurethane prepolymer canhave a number average molecular weight (Mn) of less than 50,000grams/mole, or less than 20,000 grams/mole, or less than 10,000grams/mole. The Mn can be determined using a variety of known methods.In a non-limiting embodiment, the Mn can be determined by gel permeationchromatography (GPC) using polystyrene standards.

In alternate non-limiting embodiments, the hydroxyl-containing materialfor use in the present invention can be chosen from polyether glycolsand polyester glycols having a number average molecular weight of atleast 200 grams/mole, or at least 300 grams/mole, or at least 750grams/mole; or no greater than 1,500 grams/mole, or no greater than2,500 grams/mole, or no greater than 4,000 grams/mole.

In a further non-limiting embodiment, polyether glycols for use in thepresent invention can include but are not limited to polytetramethyleneether glycol.

In a non-limiting embodiment, the hydroxyl-containing material caninclude both hydroxyl and thiol groups, such as but not limited to2-mercaptoethanol, 3-mercapto-1,2-propanediol, glycerinbis(2-mercaptoacetate) and 1-hydroxy-4-mercaptocyclohexane.

In general, polyurethanes and polyurethane prepolymers can bepolymerized using a variety of techniques known in the art. In anon-limiting embodiment of the present invention, the polymerizationprocess can include the use of an amine-containing material for curing.

Amine-containing curing agents for use in the present invention arenumerous and widely varied. Non-limiting examples of suitableamine-containing curing agents can include but are not limited toaliphatic polyamines, cycloaliphatic polyamines, aromatic polyamines andmixtures thereof. In alternate non-limiting embodiments, theamine-containing curing agent can be a polyamine having at least twofunctional groups independently chosen from primary amine (—NH₂),secondary amine (—NH—) and combinations thereof. In a furthernon-limiting embodiment, the amine-containing curing agent can have atleast two primary amine groups. In another non-limiting embodiment, theamine-containing curing agent can comprise a mixture of a polyamine andat least one material selected from a polythiol and polyol. Non-limitingexamples of suitable polythiols and polyols include those previouslyrecited herein. In still another non-limiting embodiment, theamine-containing curing agent can be a sulfur-containingamine-containing curing agent. A non-limiting example of asulfur-containing amine-containing curing agent can include Ethacure 300which is commercially available from Albemarle Corporation.

Suitable amine-containing curing agents for use in the present inventioncan include but are not limited to materials having the followingchemical formula:

wherein R₁ and R₂ can each be independently chosen from methyl, ethyl,propyl, and isopropyl groups, and R₃ can be chosen from hydrogen andchlorine. Non-limiting examples of amine-containing curing agents foruse in the present invention include the following compounds,manufactured by Lonza Ltd. (Basel, Switzerland):

-   -   LONZACURE.RTM. M-DIPA: R₁═C₃H₇; R₂═C₃H₇; R₃═H    -   LONZACURE.RTM. M-DMA: R₁═CH₃; R₂═CH₃; R₃═H    -   LONZACURE.RTM. M-MEA: R₁═CH₃; R₂═C₂H₅; R₃═H    -   LONZACURE.RTM. M-DEA: R₁═C₂H₅; R₂═C₂H₅; R₃═H    -   LONZACURE.RTM. M-MIPA: R₁═CH₃; R₂═C₃H₇; R₃═H    -   LONZACURE.RTM. M-CDEA: R₁═C₂H₅; R₂═C₂H₅; R₃═Cl        wherein R₁, R₂ and R₃ correspond to the aforementioned chemical        formula.

In a non-limiting embodiment, the amine-containing curing agent caninclude but is not limited to a diamine curing agent such as4,4′-methylenebis(3-chloro-2,6-diethylaniline), (Lonzacure.RTM. M-CDEA),which is available in the United States from Air Products and Chemical,Inc. (Allentown, Pa.). In alternate non-limiting embodiments, theamine-containing curing agent for use in the present invention caninclude 2,4-diamino-3,5-diethyl-toluene, 2,6-diamino-3,5-diethyl-tolueneand mixtures thereof (collectively “diethyltoluenediamine” or “DETDA”),which is commercially available from Albemarle Corporation under thetrade name Ethacure 100; dimethylthiotoluenediamine (DMTDA) , which iscommercially available from Albemarle Corporation under the trade nameEthacure 300; 4,4′-methylene-bis-(2-chloroaniline) which is commerciallyavailable from Kingyorker Chemicals under the trade name MOCA. DETDA canbe a liquid at room temperature with a viscosity of 156 cPs at 25° C.DETDA can be isomeric, with the 2,4-isomer range being from 75 to 81percent while the 2,6-isomer range can be from 18 to 24 percent.

Non-limiting examples of amine-containing curing agents can includeethyleneamines. Suitable ethyleneamines can include but are not limitedto ethylenediamine (EDA), diethylenetriamine (DETA),triethylenetetramine (TETA), tetraethylenepentamine (TEPA),pentaethylenehexamine (PEHA), piperazine, morpholine, substitutedmorpholine, piperidine, substituted piperidine, diethylenediamine(DEDA), and 2-amino-1-ethylpiperazine. In alternate non-limitingembodiments, the amine-containing curing agent can be chosen from one ormore isomers of C₁-C₃ dialkyl toluenediamine, such as but not limited to3,5-dimethyl-2,4-toluenediamine, 3,5-dimethyl-2,6-toluenediamine,3,5-diethyl-2,4-toluenediamine, 3,5-diethyl-2,6-toluenediamine,3,5-diisopropyl-2,4-toluenediamine, 3,5-diisopropyl-2,6-toluenediamine,and mixtures thereof. In alternate non-limiting embodiments, theamine-containing curing agent can be methylene dianiline ortrimethyleneglycol di(para-aminobenzoate).

In alternate non-limiting embodiments of the present invention, theamine-containing curing agent can include one of the following generalstructures:

In further alternate non-limiting embodiments, the amine-containingcuring agent can include one or more methylene bis anilines which can berepresented by the general formulas VII-XI, one or more aniline sulfideswhich can be represented by the general formulas XII-XVI, and/or one ormore bianilines which can be represented by the general formulasXVII-XX,

wherein R₃ and R₄ can each independently represent C₁ to C₃ alkyl, andR₅ can be chosen from hydrogen and halogen, such as but not limited tochlorine and bromine. The diamine represented by general formula VII canbe described generally as a 4,4′-methylene-bis(dialkylaniline). Suitablenon-limiting examples of diamines which can be represented by generalformula VII include but are not limited to4,4′-methylene-bis(2,6-dimethylaniline),4,4′-methylene-bis(2,6-diethylaniline),4,4′-methylene-bis(2-ethyl-6-methylaniline),4,4′-methylene-bis(2,6-diisopropylaniline),4,4′-methylene-bis(2-isopropyl-6-methylaniline) and4,4′-methylene-bis(2,6-diethyl-3-chloroaniline).

In a further non-limiting embodiment, the amine-containing curing agentcan include materials which can be represented by the following generalstructure (XXI):

where R₂₀, R₂₁, R₂₂, and R₂₃ can be independently chosen from H, C₁ toC₃ alkyl, CH₃-S- and halogen, such as but not limited to chlorine orbromine. In a non-limiting embodiment of the present invention, theamine-containing curing agent which can be represented by generalFormula XXI can include diethyl toluene diamine (DETDA) wherein R₂₃ ismethyl, R₂₀ and R₂₁ are each ethyl and R₂₂ is hydrogen. In a furthernon-limiting embodiment, the amine-containing curing agent can include4,4′-methylenedianiline.

In alternate non-limiting embodiments, amine-containing material andblowing agent can be mixed with the polyisocyanate andhydroxyl-containing materials using a variety of methods and equipment,such as but not limited to an impeller or extruder. In a non-limitingembodiment, the mixing equipment can include a mechanical stirreroperating at low pressure such as less than 20 bar. In anothernon-limiting embodiment, the components can be mixed by impingementmixing wherein the components are injected at high velocity and pressureinto a mixing chamber, and the components are then mixed in the chamberby kinetic energy. In this embodiment, the components are typicallyinjected at a velocity of from 100 to 200 meters per second, and apressure of from 20 to 3000 bar.

In alternate non-limiting embodiments, polyurethane prepolymer andoptionally polyisocyanate can be contained in a first feed of a mixingunit, amine-containing material and optionally hydroxyl-containingmaterial in a second feed and the blowing agent in a third feed; or thesecond feed can include amine-containing material and blowing agent, andoptionally hydroxyl-containing material.

In another non-limiting embodiment, the polyurethane urea can beprepared by a one-pot process by combining polyisocyanate,hydroxyl-containing material, amine-containing material and blowingagent. In a further non-limiting embodiment, the polyurethane urea canbe prepared by a one-pot process by combining polyisocyanate andpolyurethane prepolymer, optionally hydroxyl-containing material,amine-containing material and blowing agent.

In a non-limiting embodiment of the present invention, a mixing unithaving three feeds can be used in combining the polyisocyanate and/orpolyurethane, hydroxyl-containing material, amine-containing materialand blowing agent. The ingredients can be added into the feeds using avariety of configurations. In alternate non-limiting embodiments, thefirst feed of a mixing unit can contain polyisocyanate and/orpolyurethane prepolymer and the second feed can containhydroxyl-containing material, amine-containing material and blowingagent; or the second feed can contain hydroxyl functional material andamine-containing material, and a third feed can contain blowing agent;or the second feed can contain amine-containing material, and the thirdfeed can contain hydroxyl-containing material and blowing agent; or thesecond feed can contain hydroxyl-containing material, and the third feedcan contain amine-containing material and blowing agent. In a furthernon-limiting embodiment, wherein polyurethane prepolymer is present in afirst feed, the presence of hydroxyl-containing material in another feedis optional.

A blowing agent can be used in the present invention to form cells atleast partially filled with gas within the polyurethane urea material.In a non-limiting embodiment, the cells are substantially uniformlydistributed throughout the polyurethane urea material. The size of thecells can vary widely. In alternate non-limiting embodiments, a cell canbe from at least 1 micron, or at least 20 microns, or at least 30microns, or at least 40 microns; to less than 1000 microns, or less than500 microns or less than 100 microns.

In a non-limiting embodiment, the blowing agent can be water. The watercan react in-situ with isocyanate (NCO) to produce carbon dioxide. In afurther non-limiting embodiment, one or more auxiliary blowing agentscan be used in combination with the blowing agent. Suitable auxiliaryblowing agents for use in the present invention can vary widely and caninclude substances which can be substantially volatile at the reactiontemperature. The auxiliary blowing agent can be selected from thoseknown in the art. Non-limiting examples can include but are not limitedto acetone, ethyl acetate, halogen substituted alkanes such as methylenechloride, chloroform, ethylidene chloride, vinylidene chloride,monofluorotrichloromethane, chlorodifluoromethane,dichlorodifluoromethane, dichloromonofluoromethane, butane, pentane,cyclopentane hexane, heptane, diethylether, and mixtures thereof.

The amount of blowing agent used in the present invention can vary. Inalternate non-limiting embodiments, the blowing agent can be present inan amount such that a selected or desired density and/or pore volume ofthe polishing pad can be achieved. In alternate non-limitingembodiments, the density can be from 0.50 to 1.10 g/cc; the pore volumecan be from 5% to 55% based on volume of polyurethane urea material.Density can be measured using a variety of methods known to one ofordinary skill in the art. The density values recited herein aredetermined in accordance with ASTM 1622-88. Pore volume can also bemeasured using a variety of methods known to a skilled artisan. The porevolume values recited herein are determined in accordance with ASTM D4284-88, using an Autopore III mercury porosimeter manufactured byMicromeritics. In a further non-limiting embodiment, the amount ofblowing agent can be from 0 to 5% by weight of the reaction mixture.

In a non-limiting embodiment, the amine-containing material can containat least a small concentration of residual moisture or water sufficientto act as the blowing agent.

In another non-limiting embodiment, a urethane-forming catalyst and/orblowing catalyst can be used in the present invention to enhance thereaction of the polyurethane urea-forming materials, and/or acceleratethe reaction with blowing agent. In a further non-limiting embodiment,one or more materials can be used wherein each material can exhibitcharacteristics of a urethane-forming and blowing catalyst.

Suitable urethane-forming catalysts can vary, for example, suitableurethane-forming catalysts can include those catalysts that are known inthe art to be useful for the formation of urethane by reaction of theNCO and OH-containing materials. Non-limiting examples of suitablecatalysts can be chosen from the group of Lewis bases, Lewis acids andinsertion catalysts as described in Ullmann's Encyclopedia of IndustrialChemistry, 5^(th) Edition, 1992, Volume A21, pp. 673 to 674. In anon-limiting embodiment, the catalyst can be a stannous salt of anorganic acid, such as but not limited to stannous octoate, dibutyl tindilaurate, dibutyl tin diacetate, dibutyl tin mercaptide, dibutyl tindimaleate, dimethyl tin diacetate, dimethyl tin dilaurate, and mixturesthereof. In alternate non-limiting embodiments, the catalyst can be zincoctoate, bismuth, or ferric acetylacetonate.

Non-limiting examples of suitable blowing catalysts can include tertiaryamines such as but not limited to 1,4-diazabicyclo[2.2.2]octane,bis-2-dimethyl aminoethyl ether, pentamethyldiethylene triamine,triethylamine, triisopropylamine, N-methylmorpholine andN,N-dimethylbenzylamine. Such suitable tertiary amines are disclosed inU.S. Pat. No. 5,693,738 at column 10, lines 6-38, the disclosure ofwhich is incorporated herein by reference. Tertiary amine catalysts mayalso include those containing hydroxyl functionality such asN,N-dimethylethanolamine, 2-(2-dimethylaminoethoxy-)ethanol,N,N,N′-trimethyl-N′-hydroxyethyl-bisaminoether,N,N-(dimethyl)-N,N′-diisopropanol-1,3-propanediamine, andN,N-bis-(3-dimethylaminopropyl)-N-isopropanolamine.

In a non-limiting embodiment the catalyst can be chosen from phosphines,tertiary ammonium salts and tertiary amines, such as but not limited totributyl phosphine, triethylamine; triisopropylamine andN,N-dimethylbenzylamine. Additional non-limiting examples of suitabletertiary amines are disclosed in U.S. Pat. No. 5,693,738 at column 10lines 6 through 38, the disclosure of which is incorporated herein byreference.

In another non-limiting embodiment, a surfactant can be present duringpolymerization. Surfactants can influence the formation andstabilization of the at least partially gas-filled cells. In anon-limiting embodiment, the surfactant can be selected such that it hashigh surface activity for nucleation and stabilization of the cells. Inanother non-limiting embodiment, the surfactant can be selected suchthat it has good emulsifying abilities for a blowing agent. Suitablesurfactants for use in the present invention are wide and varied. In anon-limiting embodiment, a silicone surfactant can be used. The siliconesurfactant can be selected from siloxane-polyoxyalkylene copolymersurfactants. Non-limiting examples of such surfactants can include butare not limited to polydimethylsiloxane-polyoxyalkylene block copolymerswhich are available from GE Silicons Incorporated under the designationsNiax RTM. Silicone L-1800, L-5420 and L-5340; Dow Corning Corporationunder the designations DC-193, DC-5357 and DC-5315; and GoldschmidtChemical Corporation under the designations B-8404 and B-8407.

In a further non-limiting embodiment, the siloxane-polyoxyalkylenecopolymer surfactant can be represented by the following generalformula,

(XXII)

wherein x is a number from 1 to 150, y is a number of from 1 to 50, theratio of x:y is from 10:1 to 1:1 and R is an alkyl alkoxylate. Withreference to the general formula I, x can be from 10 to 50, or from 10to 42, or from 13 to 42; and y can be from 2 to 20, or from 5 to 20, orfrom 7 to 20, or from 7 to 10. The ratio of x:y can be between 2.4 and6.8.

wherein R can be an alkyl alkoxylate which can be represented by thefollowing general formula XXIII,R′O(C₂H₄O)_(m)(C₃H₆O)_(n)H  (XXIII)

wherein R′ is an alkylene group containing from 3 to 6 carbon atoms, mis a number of from 5 to 200, and n is a number of from 0 to 20, or from2 to 18. The molecular weight of R is in the range of from 400 to 4000,and the molecular weight of the surfactant represented by generalformula XXII can be from 6,000 to 50,000.

The siloxane-polyoxyalkylene copolymer surfactant can be prepared asdescribed in U.S. Pat. No. 5,691,392, column 3, line 25 through column4, line 18, which is incorporated herein by reference.

The amount of surfactant useful in the present invention can varywidely. In alternate non-limiting embodiments, the amount is such thatthe surfactant is from 0.001% to 10%, or 0.01% to 1%, or from 0.05% to0.5% by weight of the reaction mixture.

In another non-limiting embodiment, a nucleating agent can be usedduring polymerization in preparing the polyurethane urea of the presentinvention. Suitable nucleating agents for use in the present inventioncan include materials which enhance the generation of relatively smallsubstantially uniform cells. The nucleating agent can be selected fromthose known in the art. Non-limiting examples can include but are notlimited to relatively small size polymer particles (e.g., ten microns orless) such as but not limited to polypropylene, polyethylene,polystyrene, polyurethane, polyester, and polyacrylates. The amount ofnucleating agent used can vary widely. In general, the nucleating agentcan be used in an amount which is effective to generate said cells. Inalternate non-limiting embodiments, the nucleating agent can be presentin an amount of from 0.01% to 1.00%, or from 0.05% to 0.5%, by weight ofthe reaction mixture.

In a non-limiting embodiment, feeds containing polyisocyanate and/orpolyurethane prepolymer, hydroxyl-containing material, amine-containingmaterial, blowing agent and any optional additives can be directed intoa mixing unit. Optional additives can include a wide variety ofadditives known to one having ordinary skill in the art. Non-limitingexamples can include but are not limited to antioxidants, hindered amineUV stabilizers, UV absorbers, plasticizers, internal mold releaseagents, dyes and pigments. In further alternate non-limitingembodiments, any or all of the feeds can be heated to reduce theviscosity of the feeds and/or the resulting mixture. The reactionmixture exiting the mixing unit can then be poured into an open cavityto form a polishing pad. In a non-limiting embodiment, the cavity can becontrolled to a temperature of from 22° C. to 150° C., or from 60° C. to110° C.

The polishing pad of the present invention can have one or more worksurfaces, wherein “work surface” as used herein and the claims refers toa surface of the pad that can come into contact with the surface of thearticle that is to be polished and a polishing slurry. In a non-limitingembodiment, the article to be polished can be a silicon wafer. Infurther non-limiting embodiments, the work surface of the polishing padcan have surface features such as but not limited to channels, grooves,perforations and combinations thereof.

Surface features can be incorporated into the work surface of thepolishing pad by means that are known to those of ordinary skill in theart. In a non-limiting embodiment, the work surface of the pad can bemechanically modified, for example, by abrading or cutting. In anothernon-limiting embodiment, surface features can be incorporated into thework surface of the pad during the molding process, for example, byproviding at least one interior surface of the mold with raised featuresthat can be imprinted into the work surface of the pad during itsformation. Surface features can be distributed in the form of random oruniform patterns across the work surface of the polishing pad.Non-limiting examples of surface feature patterns can include but arenot limited to spirals, circles, squares, cross-hatches and waffle-likepatterns.

In a non-limiting embodiment, the polyurethane urea can comprise anabrasive particulate material. The abrasive particulate material can bedistributed substantially uniformly or non-uniformly throughout thepolyurethane urea. In alternate non-limiting embodiments, the abrasiveparticulate material can be present in an amount of less than 70 percentby weight, or at least 5 percent by weight, or from 5 percent to 65percent by weight, based on the total weight of the polishing pad.

In alternate non-limiting embodiments, the abrasive particulate materialcan be in the form of individual particles, aggregates of individualparticles, or a combination of individual particles and aggregates. Infurther alternate non-limiting embodiments, the shape of the abrasiveparticulate material can include but is not limited to spheres, rods,triangles, pyramids, cones, regular cubes, irregular cubes, and mixturesand/or combinations thereof.

In general, the average particle size of the abrasive particulatematerial can vary widely. In alternate non-limiting embodiments, theaverage particle size can be at least 0.001 micron, or at least 0.01micron, or at least 0.1 micron. In further alternate non-limitingembodiments, the average particle size of the abrasive particulatematerial can be less than 50 microns, or less than 10 microns, or lessthan 1 micron. In a non-limiting embodiment, the average particle sizeof the abrasive particulate material can measured along the longestdimension of the particle.

Non-limiting examples of suitable abrasive particulate materials for usein the present invention can include aluminum oxide, such as but notlimited to gamma alumina, fused aluminum oxide, heat treated aluminumoxide, white fused aluminum oxide, and sol gel derived alumina; siliconcarbide, such as but not limited to green silicon carbide and blacksilicon carbide; titanium diboride; boron carbide; silicon nitride;tungsten carbide; titanium carbide; diamond; boron nitride, such as butnot limited to cubic boron nitride and hexagonal boron nitride; garnet;fused alumina zirconia; silica, such as but not limited to fumed silica;iron oxide; cromia; ceria; zirconia; titania; tin oxide; manganeseoxide; and mixtures thereof. In a further non-limiting embodiment, theabrasive particulate material can be chosen from aluminum oxide, silica,cerium oxide, zirconia and mixtures thereof.

In a non-limiting embodiment, the abrasive particulate material used inthe present invention can have a surface modifier thereon. Non-limitingexamples of suitable surface modifiers can include surfactants, couplingagents and mixtures thereof. In a non-limiting embodiment, surfactantscan be used to improve the dispersibility of the abrasive particles inthe polyurethane urea. In another non-limiting embodiment, couplingagents can be used to enhance binding of the abrasive particles to thematrix of the polyurethane urea. In further non-limiting embodiments,the surface modifier can be present in an amount of less than 25 percentby weight, or from 0.5 to 10 percent by weight, based on the totalweight of the abrasive particulate material and surface modifier.

Non-limiting examples of suitable surfactants for use as surfacemodifiers in the present invention can include anionic, cationic,amphoteric and nonionic surfactants, such as but not limited to metalalkoxides, polalkylene oxides, salts of long chain fatty carboxylicacids. Non-limiting examples of suitable coupling agents for use in thepresent invention can include silanes, such as but not limited toorganosilanes, titanates and zircoaluminates. In a non-limitingembodiment, the coupling agent can include SILQUEST Silanes A-174 andA-1230, which are commercially available from Witco Corporation.

The polishing pad of the present invention can have shapes chosen frombut not limited to circles, ellipses, squares, rectangles and triangles.In a non-limiting embodiment, the polishing pad can be in the form of acontinuous belt. The polishing pads according to the present inventioncan have a wide range of sizes and thicknesses. In a non-limitingembodiment, a circular polishing pad can have a diameter ranging from3.8 cm to 137 cm. In a further non-limiting embodiment, the thickness ofthe polishing pad can vary from 0.5 mm to 5 mm.

In a non-limiting embodiment, the polishing pad of the present inventioncan have a density of from 0.5 grams per cubic centimeter (g/cc) to 1.1g/cc as measured by ASTM 1622-88. In another non-limiting embodiment,the polishing pad can have a Shore A Hardness value of at least 80, orfrom 85 to 98, and Shore D Hardness value of at least 35, or 85 or less,or from 45 to 80, as determined in accordance with ASTM D 2240.

While not intending to be bound by any theory, it is believed that whenin use, while polishing or planarizing the surface of a silicon wafer,the porosity of the work surface of the polishing pad of the presentinvention can remain substantially constant. As the work surface of thepolishing pad is worn away during, for example a polishing or padconditioning process, new surface pores are formed as those embeddedpores residing proximately below the work surface are exposed. Further,as the work surface of the polishing pad is worn away during thepolishing process, the gas contained within the at least partiallygas-filled cells can be exposed. The gas can be released into the workenvironment and the remaining void(s) can be at least partially filledwith polishing slurry.

In a non-limiting embodiment, the polishing pad can be placed directlyon the platen of a motorized polishing tool, machine, or apparatus. In afurther non-limiting embodiment, the polishing pad can be included in apolishing pad assembly, wherein a backing layer can be adhered to theback surface of the polishing pad. In a non-limiting embodiment, apolishing pad assembly can comprise:

-   -   (a) a polishing pad having a work surface and a back surface;    -   (b) a backing layer having an upper surface and a lower surface;        and    -   (c) an adhesive means interposed between and in contact with at        least a portion of the back surface of said polishing pad and at        least a portion of the upper surface of said backing layer.

In a non-limiting embodiment, the backing sheet of the polishing padassembly can be rigid or flexible, and can support or stabilize orcushion the polishing pad during polishing operations. The backing sheetcan be fabricated from materials that are known to the skilled artisan.In alternate non-limiting embodiments, the backing sheet can befabricated from organic polymeric materials, such as but not limited topolyesters, such as polyethylene terephthalate sheet, and polyolefins,such as polyethylene sheet and polypropylene sheet.

In another non-limiting embodiment, the backing sheet of the polishingpad assembly of the present invention can be a release sheet, which canbe peeled away from the adhesive means, thereby allowing the pad to beadhered to another surface, for example, the platen of a polishingapparatus, by means of the exposed adhesive means. In general, releasesheets are known to those of ordinary skill in art. In a non-limitingembodiment, the release sheet can be fabricated from paper or organicpolymeric materials, such as but not limited to polyethyleneterephthalate sheet, polyolefins, for example, polyethylene sheet andpolypropylene sheet, and fluorinated polyolefins, for example,polytetrafluoroethylene. In a further non-limiting embodiment, the uppersurface of the release sheet can comprise a release coating thereon thatcan be in contact with the adhesive means. Release coatings are wellknown to the skilled artisan. Non-limiting examples of release coatingscan include fluorinated polymers and silicones.

The adhesive can be chosen from a wide variety of adhesive materialsknown in the art. A suitable adhesive for use in the present inventioncan provide sufficient peel resistance such that the pad layersessentially remain in place during use. Further, the adhesive can beselected to sufficiently withstand shear stresses which are presentduring the polishing or planarization process and moreover, cansufficiently resist chemical and moisture degradation during use. Theadhesive can be applied using conventional techniques known to theskilled artisan. In a non-limiting embodiment, the adhesive can beapplied to a lower surface of the polishing pad and/or an upper surfaceof the backing layer which are parallel facing to one another.

Non-limiting examples of suitable adhesive means can include but notlimited to contact adhesives, pressure sensitive adhesives, structuraladhesives, hot melt adhesives, thermoplastic adhesives, and curableadhesives, such as thermosetting adhesives. Non-limiting examples ofstructural adhesives can be chosen from polyurethane adhesives, andepoxy resin adhesives; such as those based on the diglycidyl ether ofbisphenol A. Non-limiting examples of pressure sensitive adhesives caninclude an elastomeric polymer and a tackifying resin.

The elastomeric polymer can be chosen from natural rubber, butyl rubber,chlorinated rubber, polyisobutylene, poly(vinyl alkyl ethers), alkydadhesives, acrylics such as those based on copolymers of 2-ethylhexylacrylate and acrylic acid, block copolymers such asstyrene-butadiene-styrene, and mixtures thereof. In a non-limitingembodiment, a pressure sensitive adhesive can be applied to a substrateusing an organic solvent such as toluene or hexane, or from awater-based emulsion or from a melt. As used herein, “hot melt adhesive”refers to an adhesive comprised of a nonvolatile thermoplastic materialthat can be heated to a melt, then applied to a substrate as a liquid.Non-limiting examples of hot melt adhesives can be chosen fromethylene-vinyl acetate copolymers, styrene-butadiene copolymers,ethylene-ethyl acrylate copolymers, polyesters, polyamides such as thoseformed from the reaction of a diamine and a dimer acid, andpolyurethanes.

In a non-limiting embodiment, the adhesive layer can be applied to theback surface of the polishing pad and/or the upper surface of thebacking sheet, prior to pressing the polishing pad and backing sheettogether.

In alternate non-limiting embodiments, the adhesive means of thepolishing pad assembly can be selected from an adhesive assembly or anadhesive layer.

In further non-limiting embodiment, the adhesive assembly can comprisean adhesive support sheet interposed between an upper adhesive layer anda lower adhesive layer. The upper adhesive layer of the adhesiveassembly can be in contact with the back surface of the polishing pad,and the lower adhesive layer can be in contact with the upper surface ofthe backing sheet. Non-limiting examples of adhesive support sheets canbe fabricated from an organic polymeric material, such as but notlimited to polyesters, for example, polyethylene terephthalate sheet,and polyolefins, for example, polyethylene sheet and polypropylenesheet. In a further non-limiting embodiment, the upper and loweradhesive layers of the adhesive assembly can be chosen from thoseadhesives as recited previously herein with regard to the adhesivelayer. In a non-limiting embodiment, the upper and lower adhesive layerscan each be contact adhesives. In a further non-limiting embodiment, theadhesive assembly can be a two-sided or double-coated tape, such as butnot limited to double-coated film tapes, which can be commerciallyobtained from 3M, Industrial Tape and Specialties Division.

In another non-limiting embodiment, the polishing pad can be connectedto at least a portion of a second layer to produce a stacked padassembly. In a further non-limiting embodiment, the polishing pad can beconnected to at least a portion of the second layer using an adhesivematerial. Non-limiting examples of suitable adhesive materials includethose previously disclosed herein. In a further non-limiting embodiment,the second layer can comprise an adhesive assembly.

The second layer can include a variety of materials known in the art.The second layer can be selected from substantially non-volumecompressible polymers and metallic films and foils. As used herein andthe claims, “substantially non-volume compressible” means that thevolume can be reduced by less than 1% when a load of 20 psi is applied.

Non-limiting examples of substantially non-volume compressible polymerscan include polyolefins, such as but not limited to low densitypolyethylene, high density polyethylene, ultra-high molecular weightpolyethylene and polypropylene; polyvinylchloride; cellulose-basedpolymers, such as but not limited to cellulose acetate and cellulosebutyrate; acrylics; polyesters and co-polyesters, such as but notlimited to PET and PETG; polycarbonate; polyamides, such as but notlimited to nylon 6/6 and nylon 6/12; and high performance plastics, suchas but not limited to polyetheretherketone, polyphenylene oxide,polysulfone, polyimide, and polyetherimide; and mixtures thereof.

Non-limiting examples of metallic films can include but are not limitedto aluminum, copper, brass, nickel, stainless steel, and combinationsthereof.

The thickness of the second layer can vary. In alternate non-limitingembodiments, the second layer can have a thickness of at least 0.0005,or at least 0.0010; or 0.0650 inches or less, or 0.0030 inches or less.

In a non-limiting embodiment, the second layer can be flexible toenhance or increase the uniformity of contact between the polishing padand the surface of the substrate being polished. A consideration inselecting the material for the second layer can be the capability of amaterial to provide compliant support to the work surface of thepolishing pad such that the polishing pad substantially conforms to themacroscopic contour or long-term surface of the device being polished. Amaterial having said capability can be desirable for use as the secondlayer in the present invention.

The flexibility of the second layer can vary. The flexibility can bedetermined using a variety of conventional techniques known in the art.As used herein and the claims the term “flexibility” (F) refers to theinverse relationship of the second layer thickness cubed (t³) and theflexural modulus of the second layer material (E), i.e. F=1/t³E. Inalternate non-limiting embodiments, the flexibility of the second layercan be at least 0.5 in⁻¹lb⁻¹; or at least 100 in⁻¹lb⁻¹; or from 1in⁻¹lb⁻¹ to 100 in⁻¹lb⁻¹.

In a non-limiting embodiment, the second layer can have acompressibility which allows the polishing pad to substantially conformto the surface of the article to be polished. The surface of amicroelectronic substrate, such as a semiconductor wafer, can have a“wave” contour as a result of the manufacturing process. It iscontemplated that if the polishing pad cannot adequately conform to the“wave” contour of the substrate surface, the uniformity of the polishingperformance can be degraded. For example, if the pad substantiallyconforms the ends of the “wave”, but cannot substantially conform andcontact the middle portion of the “wave”, only the ends of the “wave”can be polished or planarized and the middle portion can remainsubstantially unpolished or unplanarized.

The compressibility of the second layer can vary. The term“compressibility” refers to the percent volume compressibilitymeasurement when a load of 20 psi is applied. In alternate non-limitingembodiments, the percent volume compressibility of the second layer canbe at least one percent; or three percent or less; or from one to threepercent. The percent volume compressibility can be determined using avariety of conventional methods known in the art.

In a non-limiting embodiment, the second layer is substantiallynon-volume compressible.

In another non-limiting embodiment, the second layer can distribute thecompressive forces experienced by the polishing pad over a larger areaof a sub-pad.

In another non-limiting embodiment, the second layer can function as asubstantial barrier to fluid transport between the polishing pad and asub-pad at least partially connected to the second layer. Thus, aconsideration in selecting the material comprising the second layer canbe the ability of the material to substantially reduce, minimize oressentially prevent the transport of polishing slurry from the polishingpad to a sub-pad. In a non-limiting embodiment, the second layer can besubstantially impermeable to the polishing slurry such that the sub-paddoes not become saturated with polishing slurry.

In an alternate non-limiting embodiment, the second layer can beperforated such that polishing slurry can penetrate the polishing padand second layer to wet the sub-pad. In a further non-limitingembodiment, the sub-pad can be substantially saturated with polishingslurry. The perforations in the second layer can be formed by a varietyof techniques known to the skilled artisan, such as but not limited topunching, die cutting, laser cutting or water jet cutting. The holesize, number and configuration of the perforations can vary. In anon-limiting embodiment, the perforation hole diameter can be at least1/16 inch with at least 26 holes per square inch in a staggered-holepattern.

In another non-limiting embodiment, the polishing pad of the presentinvention can be connected to at least a portion of a sub-pad forming acomposite or multi-layered structure. In a further non-limitingembodiment, the polishing pad can be connected to at least a portion ofa sub-pad using an adhesive material. Non-limiting examples of suitableadhesive materials can include those previously described herein.

In a non-limiting embodiment, a sub-pad can be used with a polishing padto increase the uniformity of contact between the polishing pad and thesurface of the substrate which is being polished. The sub-pad can bemade of a compressible material capable of imparting substantially evenpressure to the work surface of the polishing pad. Non-limiting examplesof sub-pads can include but are not limited to polyurethane andpolyurethane urea such as but not limited to polyurethane orpolyurethane urea impregnated felt; and foam sheet made of naturalrubber, synthetic rubber, thermoplastic elastomer essentially resilientfoam sheet; or combinations thereof.

In alternate non-limiting embodiments, the material of the sub-pad canbe foamed or blown to produce a porous structure. The porous structurecan be open cell, closed cell, or combinations thereof.

Non-limiting examples of synthetic rubbers can include neoprene rubber,silicone rubber, chloroprene rubber, ethylene-propylene rubber, butylrubber, polybutadiene rubber, polyisoprene rubber, EPDM polymers,styrene-butadiene copolymers, copolymers of ethylene and ethyl vinylacetate, neoprene/vinyl nitrile rubber, neoprene/EPDM/SBR rubber, andcombinations thereof. Non-limiting examples of thermoplastic elastomerscan include polyurethanes such as those based on polyethers andpolyesters, and copolymers thereof. Non-limiting examples of foam sheetcan include ethylene vinyl acetate sheets and polyethylene foam sheets;polyurethane foam sheets and polyolefin foam sheets, such as but notlimited to those which are available from Rogers Corporation, Woodstock,Conn.

In a further non-limiting embodiment, the sub-pad can include non-wovenor woven fiber mat, and combinations thereof; such as but not limited topolyolefin, polyester, polyamide, or acrylic fibers, which have beenimpregnated with a resin. The fibers can be staple or substantiallycontinuous in the fiber mat. Non-limiting examples can include but arenot limited to non-woven fabric impregnated with polyurethane, such aspolyurethane impregnated felt. A non-limiting example of a commerciallyavailable non-woven sub-pad can be Suba™ IV, from Rodel, Inc. NewarkDel.

The thickness of the sub-pad can vary. In general, the sub-pad thicknessshould be such that the stacked pad is not too thick. A stacked padwhich is too thick can be difficult to place on and take off of theplanarization equipment. Thus, in a non-limiting embodiment, thethickness of the sub-pad can be from 0.2 to 2 mm.

In a non-limiting embodiment, the polishing pad of the present inventioncan comprise a sub-pad, and the sub-pad can function as the bottom layerof the pad which can be attached to the platen of the polishingapparatus.

In a non-limiting embodiment, the sub-pad can be substantially nonporousand substantially impermeable to polishing slurry. As used herein andthe claims, the term “substantially nonporous” means generallyimpervious to the passage of liquid, gas, and bacteria. On a macroscopicscale, a substantially nonporous material exhibits few if any pores. Asused herein and the claims, the term “porous” means having pore(s) andthe term “pore(s)” refers to minute opening(s) through which matterpasses.

In a non-limiting embodiment, the sub-pad can be connected to at least aportion of the polishing pad. In a further non-limiting embodiment, thepolishing pad can be connected to at least a portion of a second layer,and the second layer can be connected to at least a portion of asub-pad.

In a non-limiting embodiment, the polishing pad of the present inventioncan be used in combination with polishing slurries which are known inthe art. Non-limiting examples of suitable slurries for use with the padof the present invention, include but are not limited to the slurriesdisclosed in U.S. patent application having Ser. Nos. 09/882,548 and09/882, 549, which were both filed on Jun. 14, 2001 and are pending. Ina non-limiting embodiment, the polishing slurry can be interposedbetween the polishing pad and the substrate to be polished. Thepolishing or planarizing process can include moving the polishing padrelative to the substrate being polished. A variety of polishingslurries are known in the art. Non-limiting examples of suitableslurries for use in the present invention include slurries comprisingabrasive particles. Abrasives that can be used in the slurries includeparticulate cerium oxide, particulate alumina, particulate silica andthe like. Examples of commercial slurries for use in the polishing ofsemiconductor substrates include but are not limited to ILD1200 andILD1300 available from Rodel, Inc. Newark Del. and Semi-Sperse AM100 andSemi-Sperse 12 available from Cabot Microelectronics Materials Division.

In a non-limiting embodiment, the window of the polishing pad of thepresent invention can be prepared using a cast-in-place process. Thisprocess can include forming an aperture in the polishing pad. Thepolishing pad can include a pair of spaced surfaces. The aperture canextend through said surfaces. The aperture can be made using a varietyof methods identified previously herein. A spacer then can be insertedin the aperture of the pad. The aperture can be sealed at one end. Innon-limiting alternate embodiments, the spacer can be temporary and canbe removed following formation of the window, or the spacer can bepermanent and remain intact following formation of the window. Thematerial, size and shape of the spacer can vary widely. In anon-limiting embodiment, the spacer can be constructed of a materialthat is at least partially transparent. In another non-limitingembodiment, the spacer can be constructed of polyester film. In general,the size and shape of the spacer can be such that it fits securely inthe aperture of the pad. In a non-limiting embodiment, the spacer can beat least partially connected to the material used to seal the opening.In a further non-limiting embodiment, an adhesive tape can be used toseal the opening and the spacer can be at least partially adhered to anadhesive portion of the tape.

The aperture above the spacer can be filled with a resin material toform an at least partially transparent panel within the aperture whichis at least partially connected to the pad. In a non-limitingembodiment, the resin can be poured into the aperture above the spacersuch that the introduction of air voids into the resin is minimized. Inanother non-limiting embodiment, the amount of resin used can be suchthat the resin level is essentially flush with a surface of the pad. Ina further non-limiting embodiment, the resin level is essentially flushwith the work surface of the pad. In another non-limiting embodiment,the bottom surface of the spacer can be essentially flush with the outersurface of the polishing pad.

In a non-limiting embodiment, the resin material can be selected suchthat the resulting window formed can be at least partially transparentto the wavelengths of the in-situ metrology instrumentation of apolishing apparatus. In a further non-limiting embodiment, the windowformed can be substantially transparent. Suitable resin materials cancomprise materials known to one having ordinary skill in the art thateither is at least partially transparent or can be made at leastpartially transparent. Non-limiting examples of resin materials for usein the present invention can include but are not limited to polyurethaneprepolymers with curative, epoxy resins with curative, ultravioletcurable acrylics, and mixtures thereof. Non-limiting examples ofsuitable materials for the resin can include thermoplastic acrylicresins, thermoset acrylic resins, such as hydroxyl-functional acrylicresins crosslinked with urea-formaldehyde or melamine-formaldehyderesins, hydroxyl-functional acrylic resins crosslinked with epoxyresins, or carboxyfunctional acrylic resins crosslinked withcarbodiimides or polyimines or epoxy resins; urethane systems, such ashydroxyfunctional acrylic resin crosslinked with polyisocyanate; diaminecured isocyanate-terminated prepolymers; isocyanate-terminatedprepolymers crosslinked with polyamines; amine-terminated resinscrosslinked with polyisocyanates; carbamate-funtional acrylic resinscrosslinked with melamine-formaldehyde resins; epoxy resins, such aspolyamide resin crosslinked with bisphenol A epoxy resins, phenolicresins crosslinked with bisphenol A epoxy resins; polyester resins, suchas hydroxyl-terminated polyesters crosslinked with melamine-formaldehyderesins or with polyisocyanates or with epoxy crosslinkers, and mixturesthereof.

In a non-limiting embodiment, the resin material can compriseamine-terminated oligomer such as VERSALINK P650 which is commerciallyavailable from Air Products and Chemicals, Inc., diamine such asLONZACURE MCDEA which is commercially available from Air Products andChemicals, Inc., and polyisocyanate such as DESMODUR N 3300A which iscommercially available from Bayer Corporation Coatings and ColorantsDivision.

In alternate non-limiting embodiments, the resin material for use in thepresent invention can include various conventional additives known inthe art. Non-limiting examples can include but are not limited toprocessing aids and degassing aids.

In a further non-limiting embodiment, the resin which can be used toform the panel in the aperture of the pad can be cured. The curingprocess can include allowing the pad containing the resin to set for aspecified amount of time at a specified temperature. The time andtemperature used to cure the window resin can vary widely and can dependon the resin material chosen to form the window. Generally, a cure timecan be chosen such that the resin is not tacky or sticky to the touch.In general, a cure temperature can be chosen such that warp ordeformation of the window which can be produced due to a curetemperature that is too low or too high does not render the padinoperable for the purpose of polishing an object. In a non-limitingembodiment, the cure time can be from 30 minutes to 48 hours, or from 18hours to 36 hours, or from 6 hours to 24 hours, or from 1 hour to 4hours. In a non-limiting embodiment, the cure temperature can be from 0°C. to less than 125° C., or from 5° C. to 120° C., or from 10° C. to115° C., or from 15° C. to 110° C., or from 22° C. to 105° C.

In a non-limiting embodiment, the aperture can be at least partiallyfilled with a resin material; and the resin material can becured/polymerized to form a polymer panel to function as the window ofthe pad. In another non-limiting embodiment, the window can include apolymer panel wherein the polymer is derived from a resin material.

Following the curing step, the spacer and the adhesive tape which wasused to seal the opening, can be removed. In an alternate non-limitingembodiment, following the curing step only the adhesive tape can beremoved and the spacer can remain in tact. In a non-limiting embodiment,the resulting window area can be made coplanar with the pad work surfaceusing a milling machine.

In a non-limiting embodiment, the backing layer can be at leastpartially connected to the work surface of the pad using an adhesivemeans as previously described herein, and a window can be formed in thispad assembly by using the cast-in-place process as previously describedherein. In this embodiment, the aperture can extend through the lowersurface of the backing layer through the adhesive means and through thework surface of the pad.

In a non-limiting embodiment, a second layer can be at least partiallyconnected to the polishing pad and, an aperture can be formed in thepolishing pad and second layer of a stacked pad as previously describedfor the polishing pad. The aperture then can be sealed on the side ofthe second layer that is not at least partially connected to thepolishing pad. The material used to seal-off the aperture can be chosenfrom a wide variety of materials known in the art. Suitable materialscan include but are not limited to adhesive materials such as adhesivetape.

In a non-limiting embodiment, the polishing pad can include a stackedpad assembly which comprises additional layers. Each additional layercan contain an aperture and the aperture(s) can be substantially alignedwith the aperture of the polishing pad. In a non-limiting embodiment, astacked pad assembly can have three layers. In a further embodiment, thelayers can include a polishing pad, a second layer and a sub-pad. Thethree layers can be at least partially connected to one another aspreviously described herein (i.e., the polishing pad connected to atleast a portion of the second layer, and the second layer connected toat least a portion of the sub-pad).

In a further non-limiting embodiment, a 22.0″ diameter SUBA IV subpadcommercially available from Rodel, Incorporated can comprise thesub-pad. An aperture can be formed in the subpad, and the aperture canat least partially align with the aperture of the second layer and theaperture of the polishing pad. In a further non-limiting embodiment, theaperture can be rectangular in shape, having dimensions of 0.5″×2.0″,being positioned with the long axis radially-oriented and centered 4″from the center of the pad. In alternate non-limiting embodiments, theaperture(s) can be formed in the layers prior to at least partiallyconnecting the layers, or the aperture can be formed following at leastpartially connecting the layers. In a non-limiting embodiment, thepolishing pad can be at least partially connected to the second layer,an aperture can be formed in the polishing pad and second layer, therelease liner of the second layer can be removed, and the exposedadhesive can be used to at least partially connect the second layer tothe SUBA IV sub-pad. An aperture can be formed in the sub-pad prior toor after at least partially connecting the sub-pad to the polishing padand second layer assembly. The aperture in the sub-pad can be at leastpartially aligned with the aperture in the other two layers. A spacercan be inserted into the aperture of the assembly, and the apertureabove the spacer can be filled with resin to form a window as previouslydescribed herein.

In another non-limiting embodiment, the window can be formed in thepolishing pad and second layer assembly as previously described herein,and the sub-pad containing an aperture then can be at least partiallyconnected to the assembly such that the aperture in the sub-pad is atleast partially aligned with the at least partially transparent panel inthe polishing pad and second layer.

Depending on the material of which the spacer is constructed, the spacercan remain in the window area or it can be removed. In alternatenon-limiting embodiments, the spacer can be constructed of a materialthat is at least partially transparent, or substantially transparent, ortransparent to at least one wavelength from 190 to 3500 nanometers, andthe spacer can remain in the window pad assembly. In anothernon-limiting embodiment, the spacer can be constructed of a materialthat may not be at least partially transparent, and the spacer can beremoved. A wide variety of known materials are suitable for use as aspacer in the present invention. Non-limiting examples can include butare not limited to polyesters, polyethylene teraphalate sheet,polyolefins such as but not limited to polyethylene sheet, polyamides,acrylics and combinations thereof. In a non-limiting embodiment of theinvention, the spacer can be removed from the window area.

In another non-limiting embodiment, the spacer can be positioned suchthat it is not flush with the outer surface of the sub-pad.

The window pad of the present invention can be used with a variety ofpolishing equipment known in the art. In a non-limiting embodiment, aMirra polisher, produced by Applied Materials Inc, Santa Clara Calif.,can be used wherein the shape of the opening is a rectangle, having asize 0.5″×2″, being positioned with the long axis radially oriented andcentered 4″ from the center of the pad. The platen for the Mirrapolisher is 20″ in diameter. A pad for use with this polisher cancomprise a circle of a 20-inch diameter having a window located in thearea as described.

In a further non-limiting embodiment, a Teres polisher commerciallyavailable from Lam Research Corporation, Fremont, Calif., can beemployed. This polisher uses a continuous belt instead of a circularplaten. The pad for this polisher can be a continuous belt of 12″ widthand 93.25″ circumference, which has a window area suitably sized andpositioned to align with the metrology window of the Teres polisher canbe such that it can be at least partially aligned with the at leastpartially transparent window in the second layer.

The present invention is more particularly described in the followingexamples, which are intended to be illustrative only, since numerousmodifications and variations therein will be apparent to those skilledin the art. Unless otherwise specified, all parts and all percentagesare by weight.

EXAMPLES Example 1

36.00 kilograms of Airthane PHP-75D polyurethane prepolymer , 1.26kilograms of Desmodur N 3300A and 0.19 kilograms of Niax L-1800surfactant were charged into the first tank of a Baule′ three-componentlow pressure dispensing machine and held at 140° F. with 15 PSI ofnitrogen pressure. This tank was mixed with low agitation. A curativemixture was prepared by melting 35.5 kilograms of Lonzacure MCDEA at atemperature of 210° F. then 5.5 kilograms of Versalink P-250 were addedwith stirring. Next, 0.21 kilograms of Niax L1800 added and stirreduntil uniformly mixed. This curative mixture was then charged into thesecond tank and held at 210° F. with 40 psi of nitrogen pressure andmixed with low aggitation. Then a mixture of 219 grams Versalink P-650,60 grams of DABCO BL-19 catalyst and 21 grams of deionized water werecharged into the third tank at ambient temperature and pressure. Thefluids of the first, second and third tanks were fed into a mixer, byconstant delivery pumps, at a weight ratio of 242 grams from the firsttank : 100 grams from the second tank : 1.80 grams from the third tank.The fluids were mixed under high agitation and dispensed into an opencircular mold having a diameter of 31 inches and a thickness of 0.090inches which had been preheated to 160° F. The open mold was placed inan oven at 160° F. for 15 minutes. After this time, the product wasremoved from the mold. Curing was continued for 18 hours at 230° F. Theproduct was then allowed to cool to ambient temperature. A double-coatedfilm tape with release liner was applied to one surface of the curedsheets. The film tape was commercially obtained from 3M as type 9609double-coated film tape.

A circular pad having a 20″ diameter was cut from the molded part. Thepad was then cut to a thickness of 0.090 inches and the upper and lowersurfaces of the pad were made parallel using a milling machine.Concentric circular grooves 0.020″ wide×0.030″ deep with a pitch of0.060″ were machined into the work surface. A window opening was thencut in the pad. The shape of the opening was rectangular, havingdimensions of 0.5″×2.0″, being positioned with the long axis radiallyoriented and centered 4″ from the center of the pad. The pad opening wassealed on the liner side with a 4″×4″ piece of 3M 9609 double-sidedtape. A spacer, constructed of 0.010″ polyester film, cut withdimensions to fit securely in the pad opening, was placed in the openingand firmly attached to the exposed adhesive of the 4″×4″ 3M 9609 tape. Awindow resin was then prepared from the ingredients listed in Table 1.TABLE 1 Ingredients Weight (grams) Charge 1 LONZACURE MCDEA 11.3VERSALINK P650 70.8 ETHACURE 100 7.7 Charge 2 AIRTHANE PHP-75D 42.0DESMODUR N 3300A 48.0AIRTHANE PHP-75D prepolymer, obtained from Air Products and Chemicals,Inc, which describes it as the isocyanate functional reaction product oftoluene diisocyanate and poly(tetramethylene glycol).DESMODUR N 3300A aliphatic polyisocyanate, obtained from BayerCorporation, Coatings and Colorants Division, which describes it as apolyfunctional aliphatic isocyanate resin based on hexamethylenediisocyanate.NIAX Silicone L-1800 was obtained from GE Silicones.LONZACURE MCDEA diamine curative, obtained from Air Products andChemicals, Inc, which describes it as methylenebis(chlorodiethylanaline).VERSALINK P250 oligomeric diamine curative was obtained from AirProducts and Chemicals, Inc.VERSALINK P650 oligomeric diamine curative, obtained from Air Productsand Chemicals, Inc, which describes it as polytetramethylene etherglycol-diamine.DABCO BL-19 catalyst, obtained from Air Products and Chemicals, Inc,which describes it as bis(2-dimethylamino ethyl) ether.ETHACURE 100, obtained from Albemarle Corporation, which describes it asdiethyltoluenediamine.

Charge 1 was added to an open stainless steel container and placed on ahot plate set at a temperature of 120° C. until the contents of thecontainer became molten. The contents were thoroughly mixed with astainless steel spatula until uniform. Charge 1 was then degassed toremove moisture and entrained air by placing the container in a vacuumoven set at 80° C. and pulling a vacuum of 1 mm to 5 mm Hg untilbubbling ceased and any foaming subsided. The container was then removedfrom the vacuum oven, Charge 2 was added to Charge 1 and mixed with aspatula until uniform. The container was then placed in a second vacuumoven at ambient temperature and a 1 mm to 5 mm Hg vacuum was pulled for5 minutes to remove any entrained air resulting from mixing.

The container of resin was then removed from the vacuum oven and aportion of the resin was carefully poured into the pad window opening,containing a spacer, so as not to introduce air voids into the resin.Sufficient resin was poured to bring the resin level flush with theupper pad surface. The resin was then allowed to cure overnight atambient conditions. After curing, the 4″×4″ piece of 3M 9609 doublesided tape and the spacer were removed. The window area was then madecoplanar with the pad work surface using a milling machine.

Example 2

A stacked pad was constructed by mounting the polishing pad assembly ofExample 1 on a 22.0″ diameter subpad. The subpad consisted of apolyurethane foam disk having a diameter of 20″ which was die cut from asheet of PORON FH 48 available from Rogers Corporation, Woodstock,Conn., having a thickness of 1.5 millimeters and a density of 0.48g/cm³. Another double-coated film tape with release liner wascommercially obtained from Adhesives Research, Inc. under the trade nameARclad 90334. The adhesive side was applied to the surface of thepolyurethane foam. A window opening was then cut into the 20″ diameterfoam pad and double-coated film tape with release liner. The shape ofthe opening was rectangular, having dimensions of 0.5″×2.0″, beingpositioned with the long axis radially oriented and centered 4″ from thecenter of the pad. Next, the release liner of the polishing pad assemblyof Example 1 was removed, exposing the adhesive. The polishing padassembly was then firmly bonded, with this adhesive, to the polyurethanefoam side of the subpad. Care was taken during mounting so that thewindow opening in the subpad was aligned with the pad window. Theremaining release liner on the subpad can be removed to permitattachment to a commercial planarizing apparatus.

1. A polyurethane urea-containing pad adapted to polish amicroelectronic substrate, said pad comprising an at least partiallytransparent window formed by a cast-in-place process, wherein saidpolyurethane urea comprises at least partially gas-filled cells, andwherein at least a portion of said at least partially gas-filled cellsis formed by an in-situ reaction.
 2. The pad of claim 1 wherein said padcomprises the reaction product of polyisocyanate, hydroxyl-containingmaterial, amine-containing material and blowing agent.
 3. The pad ofclaim 1 wherein said pad comprises the reaction product of polyurethaneprepolymer amine-containing material and blowing agent.
 4. The pad ofclaim 1 wherein said pad comprises the reaction product ofpolyisocyanate and polyurethane prepolymer, optional hydroxyl-containingmaterial, amine-containing material and blowing agent.
 5. The pad ofclaim 1 further comprising a sub-pad.
 6. The pad of claim 5 wherein saidsub-pad can be chosen from non-woven fiber mat, woven fiber mat, orcombinations thereof.
 7. The pad of claim 6 wherein said sub-pad ischosen from polyolefin, polyester, polyamide, or acrylic fibers whichhave been impregnated with a resin, and combinations thereof.
 8. The padof claim 5 wherein said sub-pad is chosen from foam sheet made ofnatural rubbers, synthetic rubbers, thermoplastic elastomers;polyurethane and polyurethane urea impregnated felt; and combinationsthereof.
 9. The pad of claim 5 wherein said pad is at least partiallyconnected to said sub-pad.
 10. The pad of claim 1 further comprising asecond layer.
 11. The pad of claim 10 wherein said second layer is atleast partially connected to said pad.
 12. The pad of claim 11 whereinsaid second layer is at least partially connected to a sub-pad.
 13. Thepad of claim 10 wherein said second layer is chosen from polyolefins,cellulose-based polymers, acrylics, polyesters and co-polyesters,polycarbonates, polyamides, plastics, and combinations thereof.
 14. Thepad of claim 10 wherein said second layer is chosen from substantiallynon-compressible polymers, metallic films and foils, and combinationsthereof.
 15. The pad of claim 1 wherein said window comprises a polymerderived from a resin material.
 16. The pad of claim 15 wherein saidresin material is chosen from polyurethane prepolymers with curative,epoxy resins with curative, ultraviolet curable acrylics, and mixturesthereof.
 17. The pad of claim 15 wherein said resin material is chosenfrom thermoplastic acrylic resins, thermoset acrylic resins, urethanesystems, epoxy resins, polyester resins, and mixtures thereof.
 18. Thepad of claim 15 wherein said resin material is chosen fromhydroxyl-functional acrylic resins crosslinked with urea-formaldehyde ormelamine-formaldehyde resins, hydroxyl-functional acrylic resinscrosslinked with epoxy resins, or carboxyfunctional acrylic resinscrosslinked with carbodiimides or polyimines or epoxy resins,hydroxyfunctional acrylic resins crosslinked with polyisocyanate,diamine cured isocyanate-terminated prepolymers, isocyanate-terminatedprepolymers crosslinked with polyamines, amine-terminated resinscrosslinked with polyisocyanates, carbamate-functional acrylic resinscrosslinked with melamine-formaldehyde resins, polyamide resincrosslinked with bisphenol A epoxy resins, phenolic resins crosslinkedwith bisphenol A epoxy resins, hydroxyl-terminated polyesterscrosslinked with melamine-formaldehyde resins or with polyisocyanates orwith epoxy crosslinkers, and mixtures thereof.
 19. The pad of claim 15wherein said resin material comprises amine-terminated oligomer,diamine, and polyisocyanate.
 20. The pad of claim 1 wherein said windowis at least partially transparent to at least one wavelength in therange of from 190 to 3500 nanometers.
 21. The pad of claim 1 whereinsaid cure temperature is from 5° C. to 120° C.
 22. The pad of claim 1wherein said cure temperature is from 10° C. to 115° C.
 23. The pad ofclaim 1 wherein said cure temperature is from 15° C. to 110° C.
 24. Thepad of claim 1 wherein said cure temperature is from 22° C. to 105° C.25. A device for polishing a microelectronic substrate, said devicecomprising: a pad having a pair of spaced surfaces, at least a portionof said pad comprising a closed-cell polyurethane urea foam havinggas-containing cells formed by an in-situ reaction; and a window in saidpad, said window comprising an aperture in said pad extending throughsaid surfaces, and a translucent panel attached to said pad within theaperture, said panel being formed in said aperture by a cast-in-placeprocess.
 26. The device of claim 25 wherein said pad further comprises asub-pad.
 27. The device of claim 25 wherein said pad comprises thereaction product of polyisocyanate, hydroxyl-containing material,amine-containing material and blowing agent.
 28. The device of claim 25wherein said pad comprises the reaction product of polyurethaneprepolymer, amine-containing material and blowing agent.
 29. The deviceof claim 25 wherein said pad comprises the reaction product ofpolyisocyanate and polyurethane prepolymer, optional hydroxyl-containingmaterial, amine-containing material and blowing agent.
 30. The device ofclaim 25 wherein said window comprises a resin material.
 31. The deviceof claim 25 wherein said resin material is chosen from polyurethaneprepolymers with curative, epoxy resins with curative, ultravioletcurable acrylics, and mixtures thereof.
 32. The device of claim 25wherein said window is at least partially transparent to at least onewavelength in the range of from 190 to 3500 nanometers.
 33. A method forproducing a polishing pad comprising an at least partially transparentwindow, comprising: a. forming a polyurethane urea-containing padwherein said polyurethane urea comprises at least partially gas-filledcells, and wherein at least a portion of said at least partiallygas-filled cells is formed in-situ; b. producing an opening into saidpad; c. inserting a spacer into said opening; d. filling said openingabove said spacer with a resin material; and e. allowing said resinmaterial to cure at a temperature of from 0° C. to less than 125° C. 34.The method of claim 33 further comprising: f. removing said spacer. 35.The method of claim 33 wherein said pad is the reaction product ofpolyisocyanate, hydroxyl-containing material, amine-containing materialand blowing agent.
 36. The method of claim 31 wherein said pad is thereaction product of polyurethane prepolymer, amine-containing materialand blowing agent.
 37. The method of claim 33 wherein said pad is thereaction product of polyisocyanate and polyurethane prepolymer, optionalhydroxyl-containing material, amine-containing material and blowingagent.
 38. The method of claim 33 further comprising at least partiallyconnecting to said pad a sub-pad; producing an opening in said sub-pad;and at least partially aligning said opening of said pad and saidopening of said sub-pad.
 39. The method of claim 33 further comprisingat least partially connecting said pad to a second layer and at leastpartially connecting said second layer to a sub-pad; producing anopening in said second layer and said sub-pad; and at least partiallyaligning said opening in said polishing pad, said opening in said secondlayer and said opening in said sub-pad.
 40. The method of claim 33wherein said resin material is chosen from polyurethane prepolymers withcurative, epoxy resins with curative, ultraviolet curable acrylics, andmixtures thereof.
 41. The method of claim 33 wherein said window is atleast partially transparent to wavelengths in the range of from 190 to3500 nanometers.
 42. The method of claim 33 wherein in step d, an amountof resin is used to fill said spacer such that said resin is flush witha polishing surface of said pad.
 43. The method of claim 31 wherein instep e said temperature for cure is from 5° C. to 120° C.
 44. The methodof claim 31 wherein in step e said temperature for cure is from 10° C.to 115° C.
 45. The method of claim 31 wherein in step e said temperaturefor cure is from 15° C. to 110° C.
 46. The method of claim 31 wherein instep e said temperature for cure is from 22° C. to 105° C.
 47. Apolishing pad having an at least partially transparent window whereinformation of said window comprises forming a polishing pad and a secondlayer, at least partially connecting said polishing pad to said secondlayer; producing an opening into said polishing pad and said secondlayer such that said opening in said polishing pad is at least partiallyaligned with said opening in said second layer; inserting a spacer intosaid opening; filling opening above said spacer with a resin material;allowing said resin material to cure at a temperature of from 0° C. toless than 125° C., and removing said spacer.